Headbox of a papermaking machine



Sheet of 2 March 25, 1969 L. E. DENNIS HEADB OX OF A PAPERMAKING MACHINE Filed Aug. 1965 m 6 33 k 4 0 4 M 4 fi f/ M, T6 1 4 W m0 m3 w 0 w w s 2 7 WI. m 2 33 2 w a 4 4 .a E s 3 3 s a w A A Ill 8 0 3 B A Z 3 2 \3 n D \fi 0 MV Y a 3 3 3 w 3 "W W 3 0 i 4 v 1\ f h 55%: b6 W mziu suo 3 1 E93 v Eats 15:5 4 a w w 4 3 4 /4 j 6 6 w %4 C O w Fag-3 Fig-4 I ATTOPNEYS f1! w March 25, 1969 L. E. DENNIS HEADBOX OF A PAPERMAKING MACHINE Sheet of2 Filed Aug. 4, 1965 INVENTOR' 4041/; E Benn/S x iz M $44.0; EZQWM% ATTORNEYS United States Patent 3,434,923 HEADBOX OF A PAPERMAKIN G MACHINE Louis E. Dennis, Clinton, Wis., assignor to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Aug. 4, 1965, Ser. No. 477,116 Int. Cl. D21f 1/02 U.S. Cl. 162-337 9 Claims This invention relates generally to papermaking machines and more particularly to a method and apparatus for improving the basis Weight profile of stock as it is delivered from the headbox to the travelling forming wire of a Fourdrinier machine.

In the usual Fourdrinier arrangement the stock is supplied, generally under pressure, to a headbox which is formed with a slice Opening overlying a travelling forming wire and from which the stock flows on the forming wire.

In order to obtain a uniform thickness of the web across the machine width it is desirable that a uniform quantity of stock be deposited on the forming wire across the entire width thereof. In other words, it is desirable that the stock flow as evenly as possible from the slice opening of the headbox to the forming wire, such that the basis weight profile of the stock as it is deposited on the forming wire is as uniform as possible.

However, because of the frictional forces to which the stock is subjected along the walls of the headbox as it flows to the slice opening, the basis weight profile of the stock as it is deposited on the forming wire may be markedly irregular. The flow rate of the stock in the center of the headbox generally exceeds that along the side walls, and therefore the thickness of the layer of stock deposited on the center portion of the forming wire generally substantially exceeds that deposited along the edges thereof. The result is that the thickness of the paper web is not uniform across the width of the machine but instead is greater at the center than at the outer portions of the forming wire.

The present invention provides a method and apparatus for ensuring substantially uniform flow of stock from the slice opening across the entire width of the forming wire, thus providing a substantially uniform basis weight profile of the web across the width of the machine.

The principles of the invention may be applied to existing as well as new headbox structures and lend themselves to automatic operation.

It is, therefore, an object of the present invention to provide a method and apparatus for improving the basis weight profile of paper web formed on a Fourdrinier machine.

It is another object of the invention to provide a headbox with means for maintaining a substantially uniform stock flow rate or velocity out of the slice opening across the entire width thereof.

Another object of the invention is to provide an improved headbox whereby the velocity of the stock flowing from the center portion of the slice opening is substantially the same as the velocity of the stock flowing from the end portions of the slice opening.

Another object of the invention is to provide a method and apparatus for increasing the velocity of stock along the side walls of a headbox relative to the velocity of the stock in the center portion thereof to maintain a substantially uniform stock velocity across the entire headbox and particularly across the slice opening.

A further object of the invention is to provide apparatus for maintaining a substantially uniform basis weight profile of stock as it is deposited on the forming wire of a Fourdrinier machine and which is adaptable to automatic operation and adjustable in response to variations 3,434,923 Patented Mar. 25, 1969 in basis weight profile across the width of the forming wire.

Yet another object of the invention is to provide an Improvement for a headbox which is simple in design and construction, inexpensive in manufacture, exceptional- 1y effective in providing a web having a substantially uniform basis weight profile, adaptable for automatic operation and easily added to existing as well as to new headbox constructions.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings, in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example only.

IN THE DRAWINGS FIGURE 1 is a sectional side view of a headbox of a Fourdrinier machine constructed in accordance with the principles of the present invention and situated in position with respect to a travelling forming wire associated therewith;

FIGURE 2 is a diagram illustrative of the basis weight profile of stock across the width of a papermaking machine which utilizes known headbox arrangements;

FIGURES 3 and 4 are similar to FIGURE 2 but illustrate substantially improved basis weight profiles available through utilization of the principles of the present invention;

FIGURE 5 is an enlarged fragmentary sectional side view of a headbox constructed according to another form of the invention;

FIGURE 6 is a diagram similar to FIGURES 3 and 4 but having particular association with the embodiment of FIGURE 5; and

FIGURE 7 is similar to FIGURE 5 but shows another form of the invention.

AS SHOWN IN THE DRAWINGS FIGURE 1 is illustrative of a typical headbox arrangement 10 of a Fourdrinier machine which has been modified according to the principles of this invention and which is particularly characterized as comprising a stock inlet 11 adapted to be connected to a source or supply of stock.

The stock is supplied under pressure and flows from the inlet 11 into the interior of the headbox indicated at 12 and thence outwardly from a slice opening 13 to be delivered to or deposited on the top surface of a travelling forming wire 14.

The headbox 10 may be of the open or closed or pressurized type, the principles of the invention being equally applicable to either arrangement. As illustrated, the headbox comprises a back wall 16 which defines, in part, the stock inlet 11, and spaced forwardly of the back wall 16 is a front wall 17 which extends, similarly to the back wall 16, transversely between a pair of vertical side walls 18, only one of which is shown in the sectional view depicted in FIGURE 1.

Another wall 19 also extends transversely between the side walls 18, that is, across the machine width, and comprises a vertical portion 20 spaced from the back wall 16 and extending in parallel relation thereto, and a horizontal portion 21 which forms the bottom wall of the headbox 10.

A forward or distal end 22 of the horizontal portion 21 is referred to as an apron and terminates on a line 23 immediately above a breast roll 24 about which is trained the forming wire 14. i

The front wall 17 of the headbox comprises a downwardly forwardly sloping portion 26 which terminates at 27 in vertical spaced relation to the forward end 23 of the apron 22. It will thus be appreciated that the slice opening 13 is bounded by the side walls 18, the forward end 23 of the apron 22 and the lower edge 27 of the front wall sloping portion 26, although the vertical dimension of the slice opening may be adjusted by means of a vertically movable slice 28.

One or more rectifier rolls as at 29 and additional components may be added to a conventional headbox, as is well understood by those skilled in the art.

FIGURE 2, in which lines corresponding with parts shown in FIGURE 1 are given similar reference characters with the suffix 11 added, is an illustrative diagram of the basis weight of stock across the width of a papermaking machine as the stock flows from the slice opening 13 of a conventional headbox thus far described. Lines 18a, 18a representthe sides of the headbox and lines 14a, 14a represent the sides of the forming wire 14. Line 13a represents the slice opening 13 of the headbox, and an irregular line 30 extends between lines 18a, 18a and represents the basis weight of the stock across the width of the forming 'wire as the stock flows from the slice opening 130 (reference numeral 13 in FIGURE 1) of the headbox.

The basis weight increases from a zero value at line 13a in the direction of the arrow and the diagram therefore illustrates that insofar as a conventional papermaking machine is concerned the basi weight of the stock at a center portion of the machine as indicated at 31 is greatest,

and the value drops off on both sides of the center portion 31, as indicated at 32, 32. Along the edges of the forming wire 14, that is, along lines 14a and 14a, the basis weight value diminishes almost to zero as indicated at 33, 33.

The reason for the diminution of the stock basis weight at the side extremities of the forming wire is clear when it is considered that as the stock flows through the headbox the velocity thereof decreases along the side walls 18a, 18a and has essentially a zero value immediately adjacent the side walls as a result of the friction forces imposed thereon. Of course the bottom wall 21 and the sloping portion 26 of the front wall 17 also impart frictional forces to the stock, but these forces are uniform across the Width of the machine and therefore do not affect the basis weight profile; that is, the configuration of line 30 in FIGURE 2.

In order to increase stock velocity along the side walls 18a, 18a of the headbox the present invention contemplates the provision of a pair of bleed openings 34, 34 (FIGURES 1 and 3) formed respectivel in the side walls of the headbox just upstream of the slice opening, upstream connoting a leftward direction along the length of the headbox as viewed in FIGURE 1.

In its simplest form, the bleed openings 34, 34 may constitute merely holes or ports extending through the side walls of the headbox and through which stock flows laterally outwardly therefrom.

Such flow of stock outwardly of the side Walls just adjacent to or immediately upstream of the slice opening serves to increase the velocity of the stock as it flows along the side walls and out of the slice opening at the two lateral ends thereof.

Illustrative of this result is the diagram shown in FIG- URE 3, wherein lines comparable to those shown in FIG- URE 2 are provided with comparable reference characters but with the suffix b added. Superimposed on profile line 30b is a solid profile line 36 which is illustrative of the basis weight profile which results from the utilization of the pair of bleed openings 38, 38.

In order not to waste the stock which flows through the bleed openings and to provide means for circulating such stock back to the inlet 11 of the headbox 10, a pair of conduits 37, 37 are connected to openings 34, 34. A pair of valves 38, 38 are mounted respectively in conduits 37, 37 to control the flow of stock therethrough and to control in substantial mea the basis weight profile as indicated at the solid line 39.;

The valves 38, 38 may be of a known motorized type and in the illustrative embodiment are connected respectively to a pair of valve actuators 39, 39 as will be understood by those skilled in the art. The actuators 39, 39 may in turn be connected to a known sensing device indicated diagrammatically at 40 situated along the path of travel of the forming wire and adapted to sense the thickness of the paper web formed thereon across the width of the Wire.

The web thickness sensing device 40 may be adapted to provide a signal to the valve actuators 39, 39 which, in turn, may control. the adjustment of the valves 38, 38 in response to variations in the basis weight profile of the web, thus improving the uniformifty of the thickness of the web across the width of the machine.

Referring again to the solid profile line 36 in FIGURE 3, it will be noted that although there has been a substantial increase in the basis weight of the stock immediately adjacent lines 18b, 181; as indicated at 41, 41 there exists a pair of indents or recesses 42, 42 immediately laterally inwardly of portions 41, 41. The recesses 42, 42 indicate that although the bleed openings 34, 34 are effective in increasing the stock velocity immediately adjacent the side walls 18b, 18b by drawing stock from the center portion of the headbox, these openings are not entirely effective in increasing the velocity of the stock somewhat laterally inwardly of the side walls 18b, 1812.

In order to overcome this defliciency it has been discovered that if an additional pair of bleed openings as indicated at reference numerals 43, 43 are provided in side walls 18b, 18b substantially upstream of bleed openings 34, 34 the velocity of the stock, and therefore the basis weight thereof, laterally inwardly of the side walls is increased.

For example, in FIGURE 4, wherein the suffix c is added to similar reference characters, the cumulative effect of bleed openings 34, 34 and 43, 43 results in a basis weight profile indicated at solid line 44, the profile lines 33, and 39 having been superimposed thereon. The addition of bleed openings 43, 43 therefore tends to fill the recesses 42, 42 of the profile line 36 and results in a substantially uniform profile line across the entire width of the forming wire.

As noted, a pair of conduits 46, 46 may be connected respectively to the bleed openings 43, 43 to perform the same functions as conduits 37, 37, and a pair of valves 47, 47 may be mounted thereon to perform in a manner similar to valves 38, 38. It will be understood that valve actuators and a web thickness sensing device may also be advantageously incorporated into the embodiment illustrated in FIGURE 4.

The openings 43, 43 may be larger than openings 34, 34, and preferably the ratio of the area of each of the openings 43 to the area of each of their respective opening 34 is in the range of about 111:1 to about 1091. For example, we have discovered that a preferred range of diameters of openings 34 is from about 1 to 2 inches, and the preferred range of diameters of openings 43 is from about 2 to 3 inches, although diameters of 1 /2 inches and 2 /2 inches are most preferred for openings 34 and 43 respectively.

In another form of the invention shown in FIGURE 5 a different arrangement of bleed openings is formed in each of the side walls 18, 18 upstream of the bleed openings 34, 34 and in this embodiment the second set of bleed means comprises a plurality of spaced bleed openings 48, 49 and 50, the centers of which are situated on a line 51 which extends at right angles to another line 52 which bisects the angle between the bottom wall 21 of the headbox and the downwardly sloping portion 26 of the front wall 17. According to this arrangement the velocity of the stock is increased adjacent the side walls 18, 18 not only near the bottom wall 21 (including the apron 22),

but instead across the entire converging zone or chamber indicated at 53 disposed between the bottom wall 21 and the front wall sloping portion 26, thereby minimizing a possible tendency of the stock to stagnate in the upper regions of zone 53.

Referring to the diagram in FIGURE 6, wherein lines similar to those in other figures have the suffix c added to their respective reference numerals, a separate conduit may be connected to each of the bleed openings 48-50 and a separate flow valve may be mounted in each of these conduits. Accordingly, conduits 54, 55 and 56 are shown connected to the bleed openings 48-50 respectively and separate flow valves 57-59 are mounted in the conduits for controlling the amount of stock bleed through the various openings. Valves 57-59 may also be of the motorized type and may be connected to separate valve actuators and sensing devices although in some instances it may be desirable to manifold conduits 54-56 and a single flow valve and valve actuator utilized to control the flow through all of the bleed openings simultaneously. Further, the valves 57-59 can be adapted to adjust the stock flow through their respective conduits in dilferent rates in response to identical signals from the sensing device.

In the embodiment of FIGURE 7 the bleed opening in each of the side walls 18 upstream of openings 34, 34 comprises an elongated slot 60 having a generally rectangular configuration with the longitudinal center line thereof extending along a line 51a which is situated at right angles to a line 52a which bisects the angle between the headbox bottom wall 21 and the downwardly sloping portion 26 of the front wall 17.

A valve plate 61 is slidably mounted on each of the side walls 18 by means of a pair of guide flanges 62, 62 for regulating the free area of the slot 60, thereby con trolling the rate of stock being bled therethrough. A valve plate actuator may be connected to the valve plate 6-1 to control the setting thereof in response to a signal from a sensing device similar to the device 40 shown in FIG- URE 3.

Thus there has been described a method and apparatus for improving the stock basis weight profile at the slice opening of a headbox whereby a substantially uniform flow rate of stock is achieved across the entire width of a papermaking machine. As a corollary, the paper web formed thereby is characterized by a substantially uniform thickness across the width of the machine, thereby correspondingly improving the quality of the paper.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably come within the scope of my contribution to the art.

Iclaim as my invention:

1. In a headbox having a pair of spaced side walls and a slice opening formed therein for delivering stock flowing through said headbox to a travelling forming wire,

a pair of bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening to elfect discharge of a portion of the stock therethrough to increase the flow of stock next to said side walls for improving the uniformity of the basis weight profile of stock across the width of the forming wire.

2. In a headbox having a pair of spaced side walls and a slice opening formed therein for delivering stock flowing through said headbox to a travelling forming wire,

a pair of bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening to effect discharge of a portion of the stock therethrough to increase the flow of stock next to said side walls for improving the uniformity of the basis weight profile of stock across the width of the forming wire, and

said slice opening a given distance laterally inwardly of said side walls, and

second bleed means formed in each of said side walls substantially upstream of said first bleed means to discharge another small portion of stock to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance, whereby the uniformity of the basis weight profile of stock flowing from the slice opening is improved across the width of the headbox.

4. In a headbox having a pair of laterally spaced side walls and a slice opening formed therein at one end thereof and across the width thereof for delivering stock flowing through said headbox to a travelling forming wire, the improvement of first bleed means formed in each of said side walls immediately upstream of and adjacent said slice opening to discharge a small portion of the stock therethrough for increasing the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls,

second bleed means formed in each of said side walls substantially upstream of said first bleed means to discharge another small portion of the stock therethrough and to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance, and means for controlling the amount of stock being bled from said first and second bleed means, whereby the uniformity of the basis weight profile of stock flowing from the slice opening is improved across the width of the headbox.

5. An elongated headbox for a papermaking machine having a stock inlet formed at one end thereof and a slice opening formed at the other end thereof for delivering stock from said inlet out of said slice opening to a travelling forming wire, said headbox comprising,

a pair of laterally spaced side walls,

a horizontal bottom wall extending between said side walls,

a front wall having a portion sloping downwardly toward said bottom wall terminating in vertical spaced relation thereto,

said bottom wall and said front: wallrdefining together with said side walls saidl slice opening, first bleed means formed in each of said side walls immediately upstream of and adjacent said slice opening to discharge a portion of the stock therethrough to increase the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls, and second bleed means formed in each of said side walls substantially upstream of said first bleed means to discharge a portion of stock therethrough to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance,

said second bleed means comprising a series of openings spaced from each other substantially along a line at right angles to a plane which bisects the angle between said bottom wall and said downwardly sloping portion of said front wall.

'6. A headbox for a papenmaking machine having a stock inlet formed at one end thereof and a slice opening formed at the other end thereof for delivering stock from said inlet out of said slice opening to a travelling forming wire comprising,

a pair of laterally spaced side walls,

a horizontal bottom wall extending between said side walls,

a front wall having a portion sloping downwardly toward said bottom Wall and terminating in vertical spaced relation thereto,

said bottom wall and said front wall defining together with said side walls said slice opening,

a pair of first bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening to discharge a relatively small quantity of stock therethrough for increasing the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls,

a pair of second bleed openings formed respectively in said side walls substantially upstream of said first bleed openings to discharge another small quantity of stock therethrough for increasing the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance,

each of said second bleed openings comprising an elongated slot extending substantially along a line situated at right angles to a plane which bisects the angle between said bottom wall and said downwardly sloping portion of said front wall, and

a pair of valve plates movably mounted respectively on said side walls for uncovering said slot incrementally for controlling the flow rate of stock being bled from said slots.

7. In a headbox having a pair of laterally spaced side walls and a slice opening formed therein at one end thereof and across the width thereof for delivering stock flowing through said headbox to a travelling forming wire,

a first pair of bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening for bleeding a small quantity of stock outwardly therethrough to increase the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls, and

a second pair of bleed openings formed respectively in said side walls substantially upstream of said first pair for bleeding another small quantity of stock to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance,

the ratio of the area of each of said second bleed openings to the area of each of said first bleed 8 openings being in the range of about 1.1:1 to 10:1.

8. In a headbox having a pair of laterally spaced side walls and a slice opening formed therein at one end thereof and across the width thereof for delivering stock flowing through said headbox to a travelling forming wire,

a first pair of circular bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening for bleeding a small quantity of stock outwardly therethrough to increase the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls, and

a second pair of circular bleed openings formed respectively in said side walls substantially upstream of said first pair for bleeding another small quantity of stock therethrough to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance,

the ratio of the diameter of each of said second bleed openings to the diameter of each of said first bleedopenings being in the range of about 1:1 to 3:1.

9. In a headbox having a pair of laterally spaced side walls and a slice opening formed therein at one end thereof and across the width thereof for delivering stock flowing through said headbox to a travelling forming wire,

a first pair of circular bleed openings formed respectively in said side walls immediately upstream of and adjacent said slice opening for bleeding a small quantity of stock therethrough to increase the flow of stock flowing from said slice opening a given distance laterally inwardly of said side walls, and

a second pair of bleed openings for-med respectively in said side walls substantially upstream of said first pair for bleeding another small quantity of stock therethrough to increase the flow of stock flowing from said slice opening a distance laterally inwardly of said side walls greater than said given distance,

the diameter of each of said second bleed openings being about 2 /2 inches and the diameter of each of said first bleed openings being about 1 /2 inches.

References Cited UNITED STATES PATENTS 2,788,719 4/1957 Bennett l62336X DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

US. Cl. X.R. 162-386. 

1. IN A HEADBOX HAVING A PAIR OF SPACED SIDE WALLS AND A SLICE OPENING FORMED THEREIN FOR DELIVERING STOCK FLOWING THROUGH SAID HEADBOX TO A TRAVELLING FORMING WIRE, A PAIR OF BLEED OPENINGS FORMED RESPECTIVELY IN SAID SIDE WALLS IMMEDIATELY UPSTREAM OF AND ADJACENT SAID SLICE OPENING TO EFFECT DISCHARGE OF A PORTION OF THE STOCK THERETHROUGH TO INCREASE THE FLOW OF STOCK NEXT TO SAID SIDE WALLS FOR IMPROVING THE UNIFORMITY OF THE BASIS WEIGHT PROFILE OF STOCK ACROSS THE WIDTH OF THE FORMING WIRE. 